5. No persons shall manufacture, convert or sell, or keep, offer or expose for sale, any arms, ammunition or military stores, except under a license and in the manner and to the extent permitted thereby. Nothing herein contained shall prevent any person from selling any arms or ammunition which he lawfully possesses for his own private use to any person who is not by any enactment for the time being in force prohibited from possessing the same; but every person so selling arms or ammunition to any person other than a person entitled to possess the same by reason of an exemption under section 27 of this Act shall, without unnecessary delay, give to the Magistrate of the district, or to the officer in charge of the nearest police-station, notice of the sale and of the purchaser's name and address.